java.awt.im
Class InputContext

Provides methods to control text input facilities such as input
methods and keyboard layouts.
Two methods handle both input methods and keyboard layouts: selectInputMethod
lets a client component select an input method or keyboard layout by locale,
getLocale lets a client component obtain the locale of the current input method
or keyboard layout.
The other methods more specifically support interaction with input methods:
They let client components control the behavior of input methods, and
dispatch events from the client component to the input method.

By default, one InputContext instance is created per Window instance,
and this input context is shared by all components within the window's
container hierarchy. However, this means that only one text input
operation is possible at any one time within a window, and that the
text needs to be committed when moving the focus from one text component
to another. If this is not desired, text components can create their
own input context instances.

The Java 2 platform supports input methods that have been developed in the Java
programming language, using the interfaces in the java.awt.im.spi package,
and installed into a Java 2 runtime environment as extensions. Implementations
may also support using the native input methods of the platforms they run on;
however, not all platforms and locales provide input methods. Keyboard layouts
are provided by the host platform.

Input methods are unavailable if (a) no input method written
in the Java programming language has been installed and (b) the Java 2 implementation
or the underlying platform does not support native input methods. In this case,
input contexts can still be created and used; their behavior is specified with
the individual methods below.

reconvert()
Asks the current input method to reconvert text from the
current client component.

void

removeNotify(Component client)
Notifies the input context that a client component has been
removed from its containment hierarchy, or that input method
support has been disabled for the component.

boolean

selectInputMethod(Locale locale)
Attempts to select an input method or keyboard layout that
supports the given locale, and returns a value indicating whether such
an input method or keyboard layout has been successfully selected.

getInstance

selectInputMethod

Attempts to select an input method or keyboard layout that
supports the given locale, and returns a value indicating whether such
an input method or keyboard layout has been successfully selected. The
following steps are taken until an input method has been selected:

If the currently selected input method or keyboard layout supports the
requested locale, it remains selected.

If there is no input method or keyboard layout available that supports
the requested locale, the current input method or keyboard layout remains
selected.

If the user has previously selected an input method or keyboard layout
for the requested locale from the user interface, then the most recently
selected such input method or keyboard layout is reselected.

Otherwise, an input method or keyboard layout that supports the requested
locale is selected in an implementation dependent way.

Before switching away from an input method, any currently uncommitted text
is committed. If no input method or keyboard layout supporting the requested
locale is available, then false is returned.

Not all host operating systems provide API to determine the locale of
the currently selected native input method or keyboard layout, and to
select a native input method or keyboard layout by locale.
For host operating systems that don't provide such API,
selectInputMethod assumes that native input methods or
keyboard layouts provided by the host operating system support only the
system's default locale.

A text editing component may call this method, for example, when
the user changes the insertion point, so that the user can
immediately continue typing in the language of the surrounding text.

Parameters:

locale - The desired new locale.

Returns:

true if the input method or keyboard layout that's active after
this call supports the desired locale.

getLocale

Returns the current locale of the current input method or keyboard
layout.
Returns null if the input context does not have a current input method
or keyboard layout or if the current input method's
InputMethod.getLocale() method returns null.

Not all host operating systems provide API to determine the locale of
the currently selected native input method or keyboard layout.
For host operating systems that don't provide such API,
getLocale assumes that the current locale of all native
input methods or keyboard layouts provided by the host operating system
is the system's default locale.

Returns:

the current locale of the current input method or keyboard layout

Since:

1.3

setCharacterSubsets

Sets the subsets of the Unicode character set that input methods of this input
context should be allowed to input. Null may be passed in to
indicate that all characters are allowed. The initial value
is null. The setting applies to the current input method as well
as input methods selected after this call is made. However,
applications cannot rely on this call having the desired effect,
since this setting cannot be passed on to all host input methods -
applications still need to apply their own character validation.
If no input methods are available, then this method has no effect.

Parameters:

subsets - The subsets of the Unicode character set from which characters may be input

setCompositionEnabled

public void setCompositionEnabled(boolean enable)

Enables or disables the current input method for composition,
depending on the value of the parameter enable.

An input method that is enabled for composition interprets incoming
events for both composition and control purposes, while a
disabled input method does not interpret events for composition.
Note however that events are passed on to the input method regardless
whether it is enabled or not, and that an input method that is disabled
for composition may still interpret events for control purposes,
including to enable or disable itself for composition.

For input methods provided by host operating systems, it is not always possible to
determine whether this operation is supported. For example, an input method may enable
composition only for some locales, and do nothing for other locales. For such input
methods, it is possible that this method does not throw
UnsupportedOperationException,
but also does not affect whether composition is enabled.

Parameters:

enable - whether to enable the current input method for composition

Throws:

UnsupportedOperationException - if there is no current input
method available or the current input method does not support
the enabling/disabling operation

isCompositionEnabled

public boolean isCompositionEnabled()

Determines whether the current input method is enabled for composition.
An input method that is enabled for composition interprets incoming
events for both composition and control purposes, while a
disabled input method does not interpret events for composition.

Returns:

true if the current input method is enabled for
composition; false otherwise

Throws:

UnsupportedOperationException - if there is no current input
method available or the current input method does not support
checking whether it is enabled for composition

reconvert

public void reconvert()

Asks the current input method to reconvert text from the
current client component. The input method obtains the text to
be reconverted from the client component using the
InputMethodRequests.getSelectedText
method. The other InputMethodRequests methods
must be prepared to deal with further information requests by
the input method. The composed and/or committed text will be
sent to the client component as a sequence of
InputMethodEvents. If the input method cannot
reconvert the given text, the text is returned as committed
text in an InputMethodEvent.

Throws:

UnsupportedOperationException - if there is no current input
method available or the current input method does not support
the reconversion operation.

removeNotify

Notifies the input context that a client component has been
removed from its containment hierarchy, or that input method
support has been disabled for the component. This method is
usually called from the client component's
Component.removeNotify
method. Potentially pending input from input methods
for this component is discarded.
If no input methods are available, then this method has no effect.

endComposition

public void endComposition()

Ends any input composition that may currently be going on in this
context. Depending on the platform and possibly user preferences,
this may commit or delete uncommitted text. Any changes to the text
are communicated to the active component using an input method event.
If no input methods are available, then this method has no effect.

A text editing component may call this in a variety of situations,
for example, when the user moves the insertion point within the text
(but outside the composed text), or when the component's text is
saved to a file or copied to the clipboard.

dispose

public void dispose()

Disposes of the input context and release the resources used by it.
Called by AWT for the default input context of each Window.
If no input methods are available, then this method
has no effect.

getInputMethodControlObject

Returns a control object from the current input method, or null. A
control object provides methods that control the behavior of the
input method or obtain information from the input method. The type
of the object is an input method specific class. Clients have to
compare the result against known input method control object
classes and cast to the appropriate class to invoke the methods
provided.

If no input methods are available or the current input method does
not provide an input method control object, then null is returned.